1. Field of the Invention
The present invention relates to a press apparatus for pressing water from a web.
More particularly, the present invention relates to a press apparatus having a fourth press and a lead-in felt for leading the web from the fourth press to the drying section.
2. Information Disclosure Statement
Many press section configurations have been proposed for progressively removing water from a formed web.
Usually, it is desirable to remove as much water as possible from the formed web during passage of the web through the press section because it is more economical to press the water from the web than to drive such water out of the web by the application of heat in a subsequent drying section.
The present invention relates to a configuration which includes a fourth press nip which is disposed downstream relative to a first nip defined between a roll couple and a subsequent second and third nip defined between a press roll and a first and second backing roll respectively. The first, second and third nip constitute a tri-nip or a tri-vent pressing arrangement. However, the present invention envisages a guide felt for guiding the web from the third nip through a fourth nip defined between a further press roll and a further backing roll.
The web emerging from the fourth press nip is guided by a lead-in felt towards a vacuum transfer roll of the dryer section so that the web can be automatically threaded into the dryer section.
In operation of the press apparatus according to the present invention, the web is doctored from the press roll subsequent to passage of the web through the third nip. The doctored web is received by a broke pit disposed beneath the press roll. A threading tail is cut from the web and guided by the guide felt through the fourth nip and the threading tail is subsequently widened to a full-width sheet.
By application of suction through a lead-in suction roll of a lead-in means or by the use of a grooved, drilled or solid covered roll, the web emerging from the fourth nip is led by a lead-in felt towards a further broke pit. The threading tail is disposed between the further press roll and the lead-in roll such that the threading tail is drawn towards a vacuum transfer roll disposed in abutting relationship with the lead-in felt. Consequently, the tail is guided around the vacuum transfer roll and is supported by the dryer felt and is guided towards the dryer section.
By the aforementioned arrangement, the manual handling at high speed required by the prior art arrangements for threading the machine is eliminated and furthermore, broke removal is permitted at two locations. Broke removal is in a downward direction thus eliminating the need for the prior art relatively complex horizontal conveyor arrangements which would be difficult if not impossible to operate efficiently at high machine speeds and production rates.
U.S. Pat. No. 4,086,131 to Rempel discloses a press apparatus having four nips but does not permit downward removal of broke prior to the second nip.
Therefore, it is a primary object of the present invention to provide a press apparatus that overcomes the aforementioned inadequacies of the prior art arrangements and that provides a considerable contribution to the art of pressing water from a paper web.
Other objects and advantages of the present invention will be apparent to those skilled in the art by a consideration of the detailed description contained hereinafter taken in conjunction with the annexed drawings and as defined by the appended claims.